1. Field of the Invention
The present invention relates to a nose deployed parachute recovery system to soft recover a finned projectile that was fired from a cannon such as an artillery piece, a tank or a mortar. More particularly, the invention pertains to an improved soft recoverable finned projectile that is fired from a smoothbore gun at maximum launch acceleration and corresponding high velocity, with little or zero spin rate. The system is most particularly useful in a 120 mm, fin-stabilized, nonspinning, high-g tank round.
It is often desired to non-destructively test the functioning of an artillery round which has been fired. Such testing is useful to check performance, launch environments and survivability. In this regard there would be a need to mount test equipment positioned in the nose section of a projectile and recover it after firing by soft landing the projectile after attaining a high apogee, and retrieve the test apparatus without damage.
2. Description of the Prior Art
It has long been desired to develop a parachute recovery system for a gun projectile, however, prior systems demonstrated a very low success rate, excessive weight and a limited useful gun firing environment. One parachute system for projectiles is disclosed in Statutory Invention Registration H150. However, this system is strictly for spin-stabilized, non-finned projectiles. In this prior art system, a high velocity test projectile is fired with a soft recovery system mounted in the projectile nose section. Such spin-stabilized, non-finned projectiles must be fired vertically and do not turn around. By its nature, a spin-stabilized projectile constantly gyroscopes and at its apogee, its nose is in the upward position and it stays in this upward position as gravity pulls the projectile back to earth. The spin-stabilized projectile does not turn-over at apogee and falls back towards earth base-end first, at which time a timing device causes the projectile nose to be jettisoned and a parachute to be deployed behind the falling projectile. The complete body section of the projectile is then soft recovered. Vertical firing of a fin-stabilized projectile with a nose mounted soft recovery system would result in the projectile turning-over at apogee and falling back towards earth nose first. Jettisoning the projectile nose and deploying a parachute into the windstream would cause a finned projectile to fly through the parachute and likely damage it. Hence, this system would not be feasible for finned projectiles since the fins would tangle and cut the parachute cords. Heretofore there were no known acceptable methods for testing performance of such a fin-stabilized, nonspinning projectile. In the present invention, a finned projectile is fired, usually in a non-vertical trajectory, and the parachute is deployed from the side, rather than the rear of the projectile. The parachute is sidewardly ejected while the projectile is still flying forward at a somewhat horizontal pitch, rather than vertically. The parachute then avoids the fins and opens when safely clear of them.
After firing, the projectiles are dimensionally unaltered and can be refired. The parachute soft recovery allows the projectile to be recovered in an essentially undamaged condition after firing, thus permitting the projectile to be examined for ruggedness. Such soft landings allow full dimensional, visual, and chemical residue analysis of the projectile. Onboard recorders can be used to measure gun bore telemetry parameters and the whole unit can be removed and reused for other tests with a short testing cycle.
The present invention allows projectile testing using full gun acceleration in all axes in the actual gun in which it will be used. This is advantageous since rail guns, air guns, and shock towers all have vastly different acceleration profiles. As an example, setback and balloting forces may be at the proper acceleration force level in a test piece, but the duration of the pulse may be wrong.
The nose-deployed parachute recovery module of this invention is an apparatus that mounts on the forward nose section of a finned projectile. This provides a technique of jettisoning a shielded parachute housing assembly sideways from the projectile nose into the incident windstream where it will be swept to the rear of the fins from which position the parachute can be opened safely and reliably. The soft recovery technique employing the nose-mounted parachute module in this invention involves firing the finned projectile at a high angle, for example 75.degree. so that the projectile velocity is reduced by drag and gravitational forces to a relatively low level at which the parachute can be deployed without risk.
During this period of reduced projectile velocity the nose mounted parachute module is activated by a timer which initiates an expulsion charge which then jettisons the windshield and parachute housing assembly which houses a pre-packaged parachute in a deployment bag. An offset spring causes the parachute housing assembly to be ejected to the side where it is caught by the incident windstream and carried rearward behind the projectile fins. A long flexible steel cable attaches the pre-packaged parachute to the projectile nose section. When the line becomes taut the parachute is pulled out of the deployment bag and the parachute is safely and reliably deployed from a position behind the projectile fins. The parachute provides a low velocity, fin first, soft landing for the projectile payload. This recovery technique can be used at a virtually unlimited projectile launch velocity since the projectile forward velocity can be reduced to the operational velocity levels of the parachute soft recovery system merely by adjusting the trajectory launch angle and a fuze timer setting.
The novel features of this invention, as well as the invention itself, both as to its organization and operation, will best be understood from the accompanying drawings, taken in conjunction with the accompanying description.